15V dual Power Supply for Preamplifier based on 7815 and 7915 regulator.This circuit will not work with external DC power supplies.The rectifier is a “full-wave voltage doubler” type, and with an input of 16VAC will provide about +/-20V DC at a current of 100mA
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This dual polarity power supply is easy to build, requires few parts, and is adjustable from 0-15 volts. It is great for powering op amp circuits, as well as other circuits that require a dual supply voltage. Link

For the work experiences general that want power supply LAB. I thinks L200 DC Variable power Circuit. May like you , because of give Volt range about 3V-15V and Current 2A normal. When , you see the circuit. May search eyes and the integrated circuit that use be number [...]